The present invention relates to an image recorder having a removable image forming case in which a photoconductive element serving as an image carrier and various image forming process devices such as a developing device and a cleaning device are detachably accommodated, the process devices surrounding the photoconductive element.
Image recorders such as an electrophotographic copier, laser printer and facsimile apparatus are extensively used today. Recently introduced in the market is an image recorder with which not only the supply of toner, or developer, but also the replacement of a photoconductive element, a cleaning device and the like are managed by a user. In this kind of image recorder mainly designed for personal use, a photoconductive element and various image forming process units such as a developing device and a cleaning device which are disposed around the photoconductive element are provided in a unitary assembly. The individual devices of the unitary assembly may be removed and replaced as needed, e.g., when a predetermined period of time expires, when any of those devices rails, when the developer runs out, or when the cleaning unit is filled with collected toner. Further, such an image recorder is divided into an upper and a lower structural body or unit at and along a paper transport path so that a paper sheet jamming the path may be removed by a user without resorting to a serviceman. This kind of structure is often referred to as a clam-shell structure. More specifically, the upper unit is loaded with predetermined process devices and openable relative to the lower unit which is loaded with other predetermined process devices, facilitating the removal of a jamming paper sheet. An image recorder of the kind described is disclosed in, for example, pending U.S. patent application Ser. No. 07/164,134, filed Mar. 4, 1988.
To further promote efficient operation of an image recorder of the type described, there has been proposed an image recorder having an image forming case which accommodates a photoconductive element, a developing device and a cleaning device removably therein, the casing itself being removably mounted in the image recorder. Supported by a body of the image recorder, the image forming case is positioned relative to the lower unit while being pressed from above by the upper unit. However, it is difficult to maintain the casing in an accurate position due to the limited strength of the casing, the accumulation of tolerances of various parts, the pressure exerted by the upper unit, etc. Any dislocation of the image forming casing effects the positional relationship between the photoconductive element, developing device, cleaning device and other process devices which are accommodated in the casing. For example, there may occur that a developing roller of the developing device fails to make accurate or uniform contact with the photoconductive element, resulting in the irregular distribution of image density and the wear of the photoconductive element.